pub mod arr {
    #[derive(Debug)]
    pub struct Array {
        arr: [u16; 4],
    }
    impl Array {
        pub fn new() -> Self {
            let mut arr = Array { arr: [1, 2, 3, 4] };
            return arr;
        }
        pub fn change_one(&mut self, index: u16, num: u16) -> () {
            self.arr[(index -1) as usize] = num;
        }
    }
}
